EP3917741B1

EP3917741B1 - Process for manufacturing and finishing improved engineered wood siding

Info

Publication number: EP3917741B1
Application number: EP20748036.9A
Authority: EP
Inventors: G. Paul Merrick; David L. Stackhouse; Lance Olson; Brian ST. GERMAIN; Tommy R. WYATT; Eric C. BILLINGS
Original assignee: Louisiana Pacific Corp
Current assignee: Louisiana Pacific Corp
Priority date: 2019-02-01
Filing date: 2020-02-03
Publication date: 2024-08-21
Anticipated expiration: 2040-02-03
Also published as: WO2020160552A1; EP3917741A4; CA3128381A1; CL2021002012A1; ES2986631T3; US20200247002A1; EP3917741A1; US12138824B2

Description

This application claims benefit of and priority to U S. Provisional Application No. 5 62/799,809, filed Feb. 1,2019 .

BACKGROUND

US2018/0126584 describes a process for producing a smooth-sided strand-based siding or wood structural panel.

FIELD OF INVENTION

This invention relates to a process for producing an engineered wood based siding, cladding or panel (e.g., manufactured with wood veneer, strands or fibers) with an improved smooth surface appearance.

SUMMARY OF INVENTION

In various embodiments, the present invention, which is defined in the appended claims, leads to an improved engineered wood product, along with several techniques and methods that, used separately or in combination, improve the actual and apparent surface quality of the improved engineered wood product. It includes manufacturing techniques to minimize the presence of sub-surface imperfections that may result in visible telegraphing on the exposed surface. In several embodiments, it also uses light diffraction through applied pixilation and a minimally textured finish to help camouflage inherent sub-surface defects. In additional embodiments, it includes the use of certain colors and paint gloss combinations. The synergistic combination of two or more of these methods significantly improve the actual and apparent surface quality and appearance.
In one exemplary embodiment, the manufacturing process is modified to comprise the addition of a "fines" surface layer (e.g., wood flour) to the mat prior to pressing. The fines layer is increased in basis weight over prior art layers. This higher basis weight fines layer helps hide telegraphing even where no deep or aggressive embossed texture is applied. The fines may be deposited in one layer or more than one layer and may be on, under or between various overlay layers. Further, the fines may be deposited in discreet particle form or may be pre-formed into a loosely bound mat that can be suitably conveyed in the manufacturing process.
One or more layers of an engineered, cellulose or non-cellulose (e.g. paper) based overlay (applied to the surface over, under, or between the fines layer) may also be added. In one embodiment, a medium basis weight paper overlay is combined with a second equal or higher basis weight paper overlay over a higher basis weight fines layer. This combination provides improved surface appearance, even with no or minimal embossing. In another embodiment, the fines are deposited between two overlays with the underlayer being a non-cellulose overlay and the top (over) layer being a cellulose-based overlay.
Smooth caul plates, having no texture/embossing, do not effectively hide subsurface defects that telegraph onto the surface, such as the outline of the wood element (e.g., strands) used to manufacture the engineered wood composite. In addition, smooth caul plates inherently produce smooth, glossy spots on the surface product, which is attributed to process heat, impregnated paper-based overlay, and variations in the underlying density. Such smooth, glossy spots cannot be totally eliminated merely by adjusting the fines layer basis weight (as discussed above), and cannot be totally hidden by using common paint finishes (e.g., exterior latex paint).
Caul plates with light embossing/texturing, which impart a minimal embossing/texture to the surface (i.e. the caul plates transfer an inverse image of the texture to the product surface) are used. The caul plate embossing pattern can take a variety of forms, such as minimal. In one embodiment, the light embossing comprises a series of small dots and dashes. This low level of embossment maintains the appearance of a smooth product surface when viewed from a normal distance but interrupts the light across the surface and camouflages any minor imperfections, such as glossy spots or a wood element outline.
In additional embodiments, an aggregate-containing paint primer or film coating may be applied. The aggregate may be a fine mineral or non-mineral based material, which provides additional light diffraction and pixilation of the surface, which further minimizes the appearance of minor surface imperfections. It may be pre-applied to (e.g., incorporated onto) the overlay, or may be applied to the product as a final finishing step after pressing. In further embodiments, the aggregate may be added to final paint or other coatings. Use of certain colors and paint gloss combinations of such coatings will further minimize the appearance of imperfections, while still providing the appearance of being smooth when viewed from a typical distance.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a perspective view of a manufactured wood product base layer with strand orientation.
Figure 2 shows Figure 1 with the addition of a fines layer (shown partially).
Figure 3 shows Figure 2 with the addition of a performance (e.g., paper) overlay (shown partially).
Figure 4 shows Figure 3 with the addition of a paint primer with functional additives (e.g., aggregate) (shown partially).
Figure 5 shows a partial cross-section (expanded) of the product of Figure 4.
Figure 6 shows an alternative partial cross-section (expanded) of the product of Figure 4.
Figure 7 shows a top view of Figure 4.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The disclosure comprises a method or process for producing an engineered wood based siding, cladding or panel (e.g., manufactured with wood veneer, strands or fibers) with an improved surface appearance. More particularly, imperfections in the surface are treated and/or hidden to provide the appearance of being smooth when viewed from typical viewing distances even under critical light conditions.
Engineered wood products, including, but not limited to, oriented-strand board (OSB), fiberboard, laminated strand lumber (LSL), plywood, or laminated veneer lumber (LVL), typically are produced by various primary (and sometimes secondary) pressing processes. Examples of such processes are in U S. Pat. Nos. 6,461,743 ; 5,718,786 ; 5,525,394 ; 5,470,631 ; and 5,425,976 ; and U.S. Patent Application No. 15/803,771 ( U.S. Pub. No. 20180126584 ).
The nature of the engineered wood manufacturing process results in inherent subsurface and surface defects or imperfections. Sub-surface defects often result in visible defects or imperfections on the surface (commonly referred to as "telegraphing"). Deeply or aggressively embossed or textured surfaces often can distract the eye from noticing these imperfections, but smooth (non-embossed or minimally embossed) surfaces are more susceptible to having this telegraphing become noticeable, especially under critical light conditions. This is a particular problem with engineered wood based smooth surface siding or cladding when installed on a building, where varying light conditions and viewing angles make undesirable surface imperfections noticeable.
As seen in Figures 1-7, present disclosure comprises an improved engineered wood product, along with several techniques and methods that, used separately or in combination, improve the actual and apparent surface quality of the improved engineered wood product. It includes manufacturing techniques to minimize the presence of subsurface imperfections that may result in visible telegraphing on the exposed surface. In several embodiments, it also uses light diffraction through applied pixilation and a minimally textured finish to help camouflage inherent sub-surface defects. In additional embodiments, it includes the use of certain colors and paint gloss combinations. The synergistic combination of two or more of these methods significantly improve the actual and apparent surface quality and appearance.
Figure 1 shows an example of a section (thickness not to scale) of a base mat or layer 10 for lap siding, with end 14 and side 16 edges, shown with the upper surface exposed. The base layer comprises a matrix of wood strands 12 in a particular orientation (in this case, oriented with respect to the long axis of the product).
In one exemplary embodiment, the manufacturing process is modified to comprise the addition of a "fines" surface layer (e.g., wood flour) to the mat prior to pressing. Figure 2 shows the section of Figure 1 with a fines layer 20 added over the upper surface of the base layer 10. While Figure 2 shows the fines layer 20 as partially covering the base layer for illustration purposes, the fines layer covers all or substantially all of the upper surface of the base layer 10.
The fines layer 20 is increased in basis weight over similar prior art layers. This higher basis weight fines layer helps hide telegraphing even where no deep or aggressive embossed texture is applied. The fines may be deposited in one layer or more than one layer and may be on, under or between various overlay layers, as described below. Further, the fines may be deposited in discreet particle form or may be pre-formed into a loosely bound mat that can be suitably conveyed in the manufacturing process.
In some exemplary embodiments, the fines (wood flour) layer basis weight can range from about 30 to about 500 pounds per thousand square feet (0.146 to 2.441 kgm^-2), more preferably from about 200 pounds to about 300 pounds per thousand square feet (0.976 to 1.465kgm^-2). In several embodiments, the fines layer basis weight is at least around 225 pounds per thousand square feet (1.099kgm^-2) or greater. In additional embodiments, the fines layer basis weight is an average of approximately 230 pounds per thousand square feet (1.123kgm²)or greater.
As seen in Figure 3, one or more layers of an engineered, cellulose or non-cellulose (e.g. paper) based overlay 30 (applied to the surface over, under, or between the fines layer or layers) may also be added. While Figure 3 shows the overlay layer 30 and fines layer 20 as partially covering the base layer (and intervening layers) for illustration purposes, each successive layer covers all or substantially all of the upper surface of the preceding layer(s).
In one embodiment, a medium basis weight paper overlay is combined with a second equal or higher basis weight paper overlay over a higher basis weight fines layer. This combination of two paper overlay layers 30 covering a fines layer 20 provides improved surface appearance, even with no or minimal embossing. In another embodiment, as seen in Figure 6, the fines layer 20 is deposited between two overlay layers 30a, b with the under (or lower) layer 30a being a non-cellulose overlay and the top (or over) 30 b layer being a cellulose-based overlay.
In one exemplary embodiment, the paper overlay comprises around 50 to 70 lb. (22.68-31.75kg) paper (industry standard weight, typically based on a 3000 sq. ft. (278.7m²) basis, with the weight being +/- 5%). In one embodiment with two overlays, the outside facing layer comprises 70 lb. (31.75kg) paper, while the inner overlay comprises a 50 lb. (22.68kg) overlay (or "cushion sheet").
The mat comprising the above layers 10, 20, 30 in various combinations is then subjected to heat and pressure in a press with caul plates to form the engineered wood product. Smooth caul plates, having no texture or embossing, do not effectively hide subsurface defects that telegraph onto the surface, such as the outline of the wood element (e g., strands) used to manufacture the engineered wood composite. In addition, smooth caul plates inherently produce smooth, glossy spots on the surface product. These are attributed to process heat, impregnated paper-based overlay(s), and variations in the underlying layer density. Such smooth, glossy spots cannot be totally eliminated merely by adjusting the fines layer basis weight (as discussed above), and cannot be totally hidden by using common paint finishes (e.g., exterior latex paint).
The present invention uses caul plates with light embossing or texturing, which impart a minimal embossing, texture or pattern to the upper surface of the outermost layer of the product (i.e., the caul plates transfer an inverse image of the texture to the product surface). The caul plate embossing or texture pattern can take a variety of forms, such as minimal (or light or shallow). In one embodiment, the light or minimal embossing comprises a series of small dots and dashes, which may be formed in lines or rows, or randomly placed. This low level of embossment maintains the appearance of a smooth product surface when viewed from a normal distance but interrupts the light across the surface and camouflages any minor imperfections, such as glossy spots or a wood element (e.g., strand) outline.
In additional embodiments, an aggregate-containing paint primer or film coating 40 may be applied, as seen in Figures 4, 5 and 7 (note that relative thickness of the layers in Fig. 5 is not to scale). The primer or film coating layer 40 may be applied in the factory, during the manufacturing process or post-manufacturing. The aggregate may be a fine mineral or non-mineral based material, which provides additional light diffraction and pixilation of the surface, which further minimizes the appearance of minor surface imperfections. It may be pre-applied to (e.g., incorporated onto) the overlay, or may be applied to the product as a final finishing step after pressing. While Figures 4 and 7 show the paint primer layer 40, overlay layer 30 and fines layer 20 as partially covering the base layer (and intervening layers) for illustration purposes, each successive layer covers all or substantially all of the upper surface of the preceding layer(s). As discussed above, Fig. 6 show an alternative embodiment where a first overlay layer 30a is applied
to the top of the base layer 10, below the fines layer 20, with a second overlay layer 30b applied over the fines layer.
In further embodiments, the aggregate may be added to the final paint application or other final coatings. Use of certain colors and paint gloss combinations of such coatings will further minimize the appearance of imperfections, while still providing the appearance of being smooth when viewed from a typical distance.
Thus, it should be understood that the embodiments and examples described herein have been chosen and described in order to best illustrate the principles of the invention and its practical applications to thereby enable one of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited for particular uses contemplated. Even though specific embodiments of this invention have been described, they are not to be taken as exhaustive, wherein the scope of protection is defined by the appended claims. There are several variations that will be apparent to those skilled in the art.

Claims

A manufacturing process for producing a strand-based product, comprising the steps of:
blending cellulosic strands (12) with one or more additives or chemicals;

forming a base mat (10) from said cellulosic strands;

applying one or more layers (20, 30, 30a, 30b) on the base mat, said one or more layers comprising:
a fines layer (20); and

at least one overlay layer (30, 30a, 30b);

applying heat and pressure to the base mat and said one or more layers in a pressing process to form a board,
characterised in that
the pressing process comprises application of a caul plate to produce a minimal embossment on the upper surface of the board; and

the manufacturing process comprises applying an aggregate-containing paint primer layer (40) to the embossed upper surface of the board.
The process of claim 1, wherein the fines layer comprises wood flour.
The process of claim 1 or claim 2, wherein said at least one overlay layer comprises a cellulose-based overlay layer.
The process of any preceding claim, wherein said at least one overlay layer comprises two overlay layers, a first overlay layer comprising a non-cellulose-based overlay layer (30a), and a second overlay layer comprising a cellulose-based overlay layer (30b).
The process of claim 4, wherein the fines layer is disposed between the first overlay layer and the second overlay layer.
The process of claim 4, wherein the fines layer is disposed under the first overlay layer and the second overlay layer.
The process of any of claims 4 to 6, wherein the first overlay layer and the second overlay layer have identical basis weights.
The process of any of claims 4 to 6, wherein the first overlay layer has a basis weight lower than a basis weight of the second overlay layer.
The process of claim 1, wherein the fines layer is disposed adjacent to the base mat and the at least one overlay layer is disposed adjacent to the fines layer opposite the base mat.
The process of any preceding claim, wherein the minimal embossment comprises a series of small dots and dashes, configured to camouflage imperfections in the surface of the board.
The process of any preceding claim, wherein the aggregate comprises fine mineral material.